(1) Field of the Invention
This invention relates to a piping travelling apparatus, and more particularly it is concerned with a piping travelling apparatus suitable for use in travelling through piping of relatively small diameter, such as gas distribution pipes, which has different levels in wall surface at pipe joints and elevations and depressions at many locations and which includes vertical or slanted pipe elements.
(2) Description of the Prior Art
Various proposals have hitherto been made to use different piping travelling apparatus to carry out maintenance and inspection inside the piping. One type of such apparatus is disclosed in Japanese Patent Unexamined Publication No. 107058/78 as a self-propelled vehicle having articulated arms. Another type is disclosed in Japanese Patent Unexamined Publication No. 123991/78 as a piping moving apparatus.
The self-propelled vehicle having articulated arms is capable of travelling while overcoming by its articulated arms any obstacle that might lie in the path of its travel can travel through not only piping but also a narrow space forming a multiple layer structure. The piping moving apparatus is intended for use in carrying out maintenance and inspection from inside heat transfer pipes of a nuclear power plant, for example, by inserting a probe for detecting flaws in the piping. The problem encountered in these systems of the prior art is that, although they are constructed to accommodate small variations in pipe diameter and negotiate gentle bends in piping, they lack the ability to travel along wavy surfaces and surfaces having changes in level and to negotiate sharp bends, so that they are unable to alter the direction of their travel by following a sharp bend or a branch at a junction. Thus, when they are used for travelling through gas distribution pipes including pipes of a T-shape or piping of small diameters having elbows bent at right angles, they would be unable to travel smoothly because moving means and tensioning means might drop into gaps in the pipe joints or catch against wall surfaces at the junctions.